The Efficiency of Window Design and Orientation
on Long-Cycle Passive Solar Heating Demands in
Residential Buildings.
‫كفاءة تصميم واتجاه الشباك على االحتياج الحراري السلبي بعيد المدى‬
‫بالمباني السكنية‬
Amjed A. Maghrabi
Head of Researches & Consultations
Assistant Professor, Department of Islamic Architecture
College of Engineering & Islamic Architecture,
Um Al-Qura University.
‫أمجد بن عبد الرحمن مغربي‬
‫رئيس قسم االستشارات والبحوث‬
‫أستاذ العمارة المساعد – قسم العمارة اإلسالمية‬
.‫كلية الهندسة والعمارة اإلسالمية – جامعة أم القرى‬
:‫المستخلص العربى‬
‫ لمنال كاكني نم اي بمديناة‬passive( ‫يختص هذا البحث ب تقييم األداء لمختلف أنواع الشبابيك (الفتحاا) ييماا يتعلاا بااألداء الحاراري السالبي‬
‫ عدد من أنواع الشبابيك (المفترضة ذا) األداء الحراري العالي تم مقارنتها مع أنواع من الشبابيك العادياة (الحالياة ياي محاولاة‬.‫ووترلوو بكندا‬
‫( لعدد من الشبابيك وثالثة اتجاها) للفتحا) تم دراكتها متضامنة االتجااه‬active) ‫لدراكة التقليل بعيد المدى من تكاليف اكتخدام ال اقة اإليجابية‬
.‫ المختص بدراكة االحتياج الحراري السلبي‬RetScreen PSH ‫الجنوبي والشمالي والغربي باكتخدام برنامج‬
‫نااتج عاان الترقيااة ماان الشااباك العااادي لااى الشااباك ذي األداء الحااراري العااالي نتاااوج ملموكااة للتقلياال ماان االحتياااج لااى اكااتخدام ال اقااة اإليجابيااة‬
،‫ تم اكترداد المبالغ التي تم نفاقها لترقية الشاباك لاى باباك ذي أداء حاراري أعلاى‬،‫ ضاية لى ذلك‬.‫وباألخص عند توجيه المبنى باتجاه الجنوب‬
‫ لعمال‬-‫ ويخلص البحث لى أن ما يحدد االختياار الساليم – اقتصااديا‬.)‫ يي أقل من عشرة كنوا‬،‫نظرا للتقليل من احتياج ال اقة الحرارية اإليجابية‬
.‫الترقية الم لوبة للشباك هما التكاليف األكاكية للترقية وعمر الشباك االيتراضي‬
Abstract:
This paper describes research conducted to evaluate the efficiency of various window components with respect
to solar heating demands of a prototype residential house in Waterloo, Canada. A number of proposed high
performance window types are compared against base-case conventional windows in attempt to trace the longcycle cutback in heating demands. Three window orientations including South, North and West facing were
considered. RetScreen passive solar heating project model was used for this purpose.
The upgrade of windows has shown a dramatic cutback in passive solar heating demands with preference to
South facing direction. Initial cost of window upgrade is reimbursed, due to reduction of active solar heating
cost, in less than ten years depending on the type of window selected. It is concluded that the economical
upgrade of a window depends on the initial installation cost required for the upgrade and the project life.
KEYWORDS: window, window orientation, solar, passive solar heating, cost.
1
(4). The design of window thus
must be given greater concern being
the prime source of passive heating
compared
to
other
building
components.
The work in hand compares a
number of window types (Appendixa) for a proposed house at Waterloo,
Canada. The site complex contains
a number of prototype single family,
one storey town house designed with
passive solar principles (Figure 1).
As shown in figure 1, the house
contains a number of apertures
(windows and patio doors) scattered
at various elevations. Dimensions of
these apertures are shown in
Appendix-a.
1. Introduction
Accessing
thermal
comfort
solutions in architecture requires a
number of strategies.
Amongst
these; efforts are focused on the
utilization of active and passive
heating and cooling techniques to
achieve the desired level of
occupant's comfort. With the arise
debate concerning tumbling active
energy techniques within buildings
due to its economical causes
associated with energy waste,
passive solutions are increasingly
implemented. Passive solutions are
more environmentally friendly and
have
economical
privileges
comparing to former technique.
Passive heating occurs due to
number of factors including solar
gains and other radiating resources
of
heat
around
building.
Alternatively, sources of heat within
building are limited to heat
transferred through thermal envelop,
apertures, occupants as well as
equipment
(such
as
kitchen
appliances). Amongst these, passive
solar heating (PSH) is considered the
most significant, i.e. heat penetrating
through external doors and windows
(1), (2), (3), (4), (5). Selection and
orientation of windows will
significantly control the annual
heating demand (3). In addition,
high-performance windows can
require less than half the heating
energy necessary for a space when
compared to conventional windows
(6).
Beside
pleasant
living
environment, passive solar designs
can also provide a better use of
natural daylight for lighting purposes
N
Bedroom
4*3
Bedroom
4*4
Dining
Living
4*6
Figure 1. The proposed prototype single
family, one storey town house, Waterloo,
Canada
2
A
number
of
detailed
investigations are carried out
concerning the use of highperformance windows in comparison
with conventional window types.
Full details of house components
and apertures various specifications
are examined using a project model
named by RetScreen passive solar
heating (7). The model is used to
evaluate the energy production (or
savings) and financial performance
associated with energy efficient
window use. Passive solar Heating
systems along with the project
model applications are discussed
next. A full detail of the proposed
house is highlighted later followed
by the methodological approach and
the discussion of the results.
windows are not as thermally
insulating as the building walls.
Buildings envelop acts as solar
heat storage that reduces the need for
heating in cold seasons.
For
buildings with modest window area,
lightweight construction of wood or
steel frame walls with gypsum board
offers sufficient thermal mass to
store solar gains and prevent
overheating on cold sunny days.
When compared to heavy materials
such as stone or concrete, the former
choice has significance in preserving
heat while the later releasing it
slowly overnight (9), (10), (11). The
thermal mass of the building
construction is crucial for passive
solar heating systems with large
window area. Other sources of heat
are less effective in the contribution
of heat when compared to solar heat
(12).
2. Passive Solar Heating
Systems
Passive solar heating is best
applied to buildings where heating
demand is high relative to cooling
demand (2), (8). As mentioned
earlier, the prime element in passive
solar heating systems is windows.
The transmission of solar radiation
allows energy to enter the building
and warm interior spaces whilst heat
is not easily transmitted back
outdoors. The phenomenon of
greenhouse effect is particularly
useful for supplying heating energy
in the winter.
Thus, window
dimensions, components, thermal
properties
and
orientations
contributes significantly to the
fraction of radiation piercing through
(1),(2),(3),(5).
Unfortunately,
3. Solar Heating Project
Modsel
Solar energy contribution through
an opening encounters a number of
complications
in
the
real
environment. Some of these are
related to the physics of heat
transmitting through an opaque
envelope and others are related to
the aperture and surroundings.
Calculation method or measuring
technique selected is considerably
important to decide the optimum
technique for a specific task.
Theoretical
approaches
concerning passive solar heating can
be used to evaluate the energy
production (or savings) and financial
performance associated with energy
3
efficient window use. Maghrabi
(13)
has
compared
various
measuring techniques and concluded
that theoretical approach has an
advantage at early stages of design
where a number of cases could be
examined, and parameters are
controlled. The technique was led
be many researchers as it is
beneficial in time and cost. In this
approach, assumptions are employed
to answer some of the complexities
accruing in practice since the full
understanding of these complexities
is not yet complete (14).
One of the models applied to
assess the accuracy of the calculated
energy flow is found in the work of
Arasteh et.al.(5). The model
examines the window configurations
and its effectiveness with respect to
energy and thermal comfort.
Nevertheless, the model does not
consider the annual energy cost
saving. HOT2-XP is another energy
model which is the quick entry
version of Natural Resources
Canada’s (NRCan’s) (15). The ER
method is a Canadian standard that
was developed based on hourly
energy
simulations
(8).
Additionally,
REDFEN
model
solution is used to predict energy
performance of fenestration on
residential buildings (3). The work
in hand was carried using RetScreen
Passive Solar Heating Project Model
(7).
The Model can be used to
evaluate the energy production (or
savings) and financial performance
associated with energy efficient
window use (7), (12). The model is
intended for low-rise residential
applications, although it can be used
for small commercial buildings, and
it applies anywhere in the world
where there is a significant heating
load. A number of projects are
investigated using RetScreen project
model including those found in
Canada, USA, Germany, and
recently in Japan. Validations of the
project model in hand and various
model equations involved are found
in RetScreen PSH manual (12) for
further investigation.
Basically, the model can be used
to determine how efficient window
use can affect building energy use in
four ways:
1. Increased solar heat gains to the
building through larger and
better-oriented windows;
2. Reduced heat loss through more
insulating windows;
3. Increased or reduced solar gains
through the use of appropriate
glazing; and
4. Reduced cooling energy demand
due to improved shading.
3.1. Adjustment of Window
Thermal Properties
The
software
incorporates
database, which includes more than
1,000 windows that have thermal
performance ratings. It adjusts the
window thermal properties for the
actual window sizes using method
recommended by Baker and Henry
(16). Dimensions of samples used to
rate windows, according to Canadian
standards, with respect to their Uvalues and solar heat gain
coefficients (SHGC) are found in
4
Appendix-a. In the model it is
assumed that all windows of the
same orientation have the same
SHGC unless different type of
window was used (7), (12).
The
utilization
factor
is
calculated according to methods
developed by Barakat and Sander
(17). Values for a 5.5°C temperature
swing are used in the software
program (this is likely the maximum
swing that could be tolerated in a
passive solar house) (7).
The
resulting utilization factor indicates
the proportion of the transmitted
solar gains that are utilized to offset
heating load.
Heating energy savings are
calculated for each month as the
difference between the energy
required to heat the building in the
base case and in the proposed case.
The energy savings over the heating
season are the sum of the monthly
energy savings:
3.2. Heating Energy Savings
Two terms are evaluated each
month to determine the net heating
demand: heating demand (gross) and
usable solar heat gains. Third term,
internal gains, although part of each
monthly evaluation, is assumed
constant throughout the year. The
model determines the difference in
energy consumption between the
proposed passive solar building and
an identical building but without the
passive solar features (i.e. the “base
case”).
The monthly heating
demand and usable solar gains will
be different between the base case
and proposed buildings because of
differences in window properties and
orientations.
Building monthly
heating demand is assumed to vary
linearly with outdoor temperature
and is based on typical house heat
loss coefficients.
The increase in solar heat gains
obtained in the proposed case
configuration is the sum of two
terms: first, the associated increase
in solar gains due to higher
transmission of short-wave radiation
through the glazing, and second, the
re-distribution of window area that
changes the total amount of solar
energy captured by the windows due
to their orientations. The seasons
are considered six-month periods
corresponding
to
the
sun’s
movement.
3.3. Cooling Energy Savings.
One of the tradeoffs associated
with increased solar gains is the
additional heat that may contribute
to cooling energy demand in the
summer months. To determine
annual
energy
savings,
the
detrimental effects of increased solar
heat gain must be assessed. For
heating-dominated climates, the
conductive heat gain through
windows in the summer is very
small relative to the solar gains and
can be ignored (18); therefore the
additional cooling requirement is
determined only from the increased
solar gain.
3.4. Annual Energy Savings
Annual energy savings, referred
to in the model as renewable energy
delivered, , are obtained by simply
5
summing heating and cooling energy
savings. Finally, the model also
calculates the peak heating or
cooling load (power) reductions,
which indicate to the user
opportunities to reduce the capacity
of the conventional heating system
or that of the air-conditioning
system. Appendix-b demonstrates
the flowchart of the PSH energy
model(7).
there are three main types; singleglazed, double and triple-glazed.
The sources of information for the
window SHGC obtained from the
project model data base matches
those found in the ASHRAE
Handbook-Fundamentals (20). The
U-value is a measure of the heat
transmission of the
window
(Appendix-a). It is assumed that all
windows of the same orientation
have the same U-values (12). Unit
cost for each type of windows as
they are involved in the process to
acquire the life-cycle cost of energy
demand for passive heating are
entered in the model. The insulated
glass units (IGU) is double-glazed
with a single low-e film plus argon
gas fill (DC-Le-A) and the high
performance IGU is triple-glazed
with double low-e films fill (TC-Le)
are examined and compared against
the double-glazed (DC) and singleglazed (SC) types. Low-e film
material was proved to provide
greater savings with respect to high
solar heat (2).
The orientations examined are
limited to the selected most
appropriate window types obtained
from the model. Allocating the
house into three various orientations
including south, north and westfacing as shown in Table-1. It is
worth mentioning that about Sixty
five percent of the window area is on
the front elevation (Table 1). Heat
generated by the sun could have
disadvantages during summer for
larger apertures. Nevertheless, since
average temperature does not exceed
20C (Table 2) the additional heat
4. The house
The proposed house consists of a
living space, two bedrooms, dining,
and other amenities including
kitchen, bathroom, toilet and storage
(Figure 1). As mentioned before, the
house is designed with passive solar
principles as an attempt to analyze
the long term cutback in heating
demands.
The insulation level used by the
wall thickness and the thermal
resistance of the insulation material
used in the walls. At this proposed
dwelling, a high insulation level
building would have walls with at
least 200mm of fibrous insulation
(RSI > 4.5 m²·°C/W). Appendix-c
shows the general parameters that
are required to run the model.
As far as apertures were
concerned, an attempt to intensively
examine the various components of
these apertures and how they
contribute to the house efficiency
with respect to passive heating
demand.
The regulations of
Canadian Standard Association
(CAN/CSA A440.2) (19) set the
types windows with respect to their
thermal properties.
Apparently,
6
provided by the sun can add little
segment to air-conditioning loads.
This problem can be alleviated by
the use of shading elements.
windows as well as the correct use
of energy efficient windows with
varieties of thermal properties.
Sensitivity analysis is performed to
help determine which parameters are
critical to the financial viability of a
project and, meanwhile,
to
improve the performance of the
building envelope with positive
environmental benefits.
Table 1. Various orientations examined
with respect to window configurations
5. Methodological Approach
Window Type: Two different
cases will take place comparing:
1. Single-glazes (SC) window type
(base model) with respect to three
window types (proposed models):
a. Double-glazed Clear Window
type (DC)
b. Double-glazed, Low-e, Argon
(DC-Le-A)
c. Triple-glazed, Low-e, (TCLe)
2. Double-glazed clear (DC) window
type (base model) with respect to
two other types (proposed models):
a. Double-glazed, Low-e, Argon
(DC-Le-A)
b. Triple-glazed, Low-e, (TCLe)
3. Orientation, as three orientations
were examined for the selected
model;
a. Front elevation facing south
b. Front elevation facing west
c. Front elevation facing north
Initial cost of unit and installing
at each window upgrade (Appendixc) is considered in the project model
to trace the year to positive cash
flow and long cycle cut back in
energy demands.
Table 2. Various orientations examined
with respect to window configurations
In conclusion, passive solar
design in hand evolved proper
orientation of buildings and proper
location and surface area for
7
Table 3. Results of upgrading
Single-glazed (base case) with respect to
other window types
Window Type
DC-Le-A
$
(2,035)
706
741
778
817
858
901
946
993
1,043
1,095
1,149
1,207
1,267
1,331
1,397
1,467
1,540
1,617
1,698
1,783
1,872
1,966
2,064
2,167
2,276
2,390
2,509
2,635
2,766
2,905
$
(2,035)
(1,329)
(588)
190
1,006
1,864
2,765
3,711
4,703
5,746
6,841
7,990
9,197
10,464
11,795
13,192
14,659
16,200
17,817
19,515
21,298
23,171
25,137
27,201
29,368
31,644
34,034
36,543
39,178
41,944
44,848
Saving
Cumulative
$
(4,428)
780
819
860
903
948
996
1,046
1,098
1,153
1,211
1,271
1,335
1,401
1,471
1,545
1,622
1,703
1,789
1,878
1,972
2,070
2,174
2,283
2,397
2,517
2,642
2,775
2,913
3,059
3,212
$
(4,428)
(3,647)
(2,828)
(1,968)
(1,064)
(116)
880
1,926
3,024
4,177
5,387
6,658
7,993
9,394
10,866
12,411
14,033
15,736
17,525
19,403
21,375
23,445
25,619
27,902
30,298
32,815
35,458
38,232
41,145
44,204
47,416
Totlal initital cost
Year to positive cash flow
After 10 years
Cumuative cashflow
After 20 years
After 30 years
DC-Le-A
$
(5,951)
(5,171)
(4,351)
(3,491)
(2,588)
(1,639)
(643)
402
1,500
2,653
3,864
5,135
6,470
7,871
9,342
10,887
12,510
14,213
16,001
17,879
19,851
21,922
24,096
26,378
28,775
31,292
33,934
36,709
39,622
42,681
45,893
Ye
TC-Le
Saving
Cumulative
Saving
Cumulative
$ Window Type
$
$
$
DC-Le-A
(2,393)
(2,393) TC-Le
(3,916)
(3,916)
#
a0
r
Saving
1
Cumulative
Cumulative Saving
288
(2,105)
$
$
$
302
(1,803)
(3,916)
(2,393)
(2,393)
317
(1,486)
348
(2,105)
288
(1,153) 365
302333 (1,803)
317350 (1,486) (803) 383
333367 (1,153) (436) 403
350385 (803) (50) 423
367405 (436) 354 444
(50) 779 466
385425
405446 3541,226 489
425469 7791,694 514
446492 1,2262,186 540
469517 1,6942,703 567
595
2,186
492
542
3,245
625
2,703
517
570 3,2453,815 656
542
570598 3,8154,413 689
598628 4,4135,041 723
628659 5,0415,700 759
659692 5,7006,392 797
692727 6,3927,119 837
727763 7,1197,882 879
763801 7,8828,684 923
801841 8,6849,525 969
841884 9,525
10,4091,017
884
928 10,409
11,3371,068
1,122
11,337
928
974
12,311
1,178
12,311
974
1,023 13,334
13,3341,237
1,023
1,074
14,407
1,299
14,407
1,074
1,128 15,535
15,5351,363
1,128
1,184 16,719
16,7191,432
1,184
#
2
0
3
1
24
35
46
57
68
79
810
911
10
12
11
13
12
14
13
15
14
16
15
17
16
18
17
19
18
20
19
20
21
21
22
22
23
23
24
24
25
25
26
26
27
27
28
28
29
29
30
30
348
$
365
(3,916)
383
(3,568)
403
(3,203)
423
(2,820)
444
(2,417)
466
(1,994)
489
(1,550)
(1,084)
514
(595)
540
567(81)
595459
1,025
625
1,620
656
2,245
689
2,900
723
3,589
759
4,312
797
5,071
837
5,868
879
6,706
7,584
923
8,507
969
9,476
1,017
10,494
1,068
11,562
1,122
12,684
1,178
13,861
1,237
15,098
1,299
16,397
1,363
17,760
1,432
19,192
(3,568)
(3,203)
(2,820)
(2,417)
(1,994)
(1,550)
(1,084)
(595)
(81)
459
1,025
1,620
2,245
2,900
3,589
4,312
5,071
5,868
6,706
7,584
8,507
9,476
10,494
11,562
12,684
13,861
15,098
16,397
17,760
19,192
Window Type
Window Type
TC-Le
DC-Le-A DC-Le-A
TC-Le
-3,916.00 -3,916.00
-2,392.50-2,392.50
cost cost
initital
Totlal
Totlal
initital
9.20
7.10
flow flow
cash cash
to positive
Year
Year
to positive
7.10
9.20
459
10 years
After After
10 years 1,226
1,226
459
Cumuative cashflow
7,584
7,119
After 20 years
Cumuative cashflow
After 20 years
7,119
7,584
19,192
16,719
After 30 years
summary
Financial
Financial
summary
Years
Double
Double wih low-e
16,719
30
26
28
18
20
14
16
8
10
12
6
4
After 30 years
2
0
$
$
(5,951)
780
819
860
903
948
996
1,046
1,098
1,153
1,211
1,271
1,335
1,401
1,471
1,545
1,622
1,703
1,789
1,878
1,972
2,070
2,174
2,283
2,397
2,517
2,642
2,775
2,913
3,059
3,212
Cumulative
Window Type
DC
DC-Le-A
TC-Le
-2,035 -4,427.50
-5,951
2.80
5.10
6.60
6,841
5,387
3,864
21,298
21,375
19,851
44,848
47,416
45,893
Financial summary
50,000
45,000
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
0
-5,000
-10,000
Window Type
TC-Le
Saving
22
24
#
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Cumulative
ar
Saving
Ye
ar
Ye
DC
Table 4. Results of upgrading
Double-glazed (base case) with respect
to other window types.
20,000
Triple
15,000
Figure 2. Regression curves of
upgrading Single-glazed (base case) with
respect to other window types.
$
10,000
5,000
30
28
26
24
22
20
18
16
14
12
8
10
6
4
2
0
0
-5,000
6. Discussion
-10,000
1.
Years
6.1. Window Type
Single-glazed (SC) as a based
model: As shown in Figure (2)
and Table (3), three cases took
place for the proposed dwelling.
Double wih low-e
Triple
Figure 3. Regression curves of
upgrading Double-glazed (base case)
with respect to other window types.
8
19,192
There is a clear improvement for
the upgrade from single-glazed
(SC) to double-glazed (DC)
window type. The initial cost of
this upgrade was reimbursed
three years later. In other words,
the year to positive cash flow was
shown roughly after two years
and
nine
months
after
installation.
Additionally, the
cumulative cash flow after 10, 20
and 30 years was $6,841, $21,298
and $44,848 respectively. The
fraction of cash flow is even
more with the upgrade to type
DC-Le-A or TC-Le. It is worth
mentioning that after twenty year
of use, the cumulative cash flow
for the three upgrades reaches
nearly $20,000 although the year
to positive cash flow varies
(Table 3). The regression curve
of the year to positive cash flow
ranged from two to six and half
years for the three types. In one
hand, the comparison shows an
evident advantage to the upgrade.
On the other hand, it shows that
SC window type has a
disadvantage to passive solar
heating when implemented in
these climatic regions.
temperature degrees reaches below
freezing point (8), (19), (21).
2. Double-glazed (DC) as a base
model: The two proposed types
are Dc-Le-A and TC-Le as
shown in Figure (3) and Table
(4). A number of results are
derived from the comparison:
‫ ڤ‬Initial cost for upgrade to DcLe-A type is $2,392. This
number is increase with 40%
when TC-Le type is selected.
‫ ڤ‬Dc-Le-A has almost 2 years to
cash flow privilege to the other
type.
‫ ڤ‬With respect to the cumulative
cash flow, small fraction of
improvement was recorded to
TC-Le, after 20 years of use.
This fraction is even increase
with 25% when reaching 30
years as shown in Figure 3 and
Table 4.
‫ ڤ‬So, if the replacement of this
window would occur after 20
years, it is more economical to
use Dc-Le-A type since initial
cost was less.
‫ ڤ‬If replacement would occur
later, then the proper decision
for the proposed window type
would be TC-Le as illustrated
in Figure 3 and Table 4.
In conclusion, with consideration
to current climate conditions, the
decision to implement SC window
type is bounded with considerable
fraction of uncertainty. This assures
recommendations set by ASHRAE
Fundamentals
and
Canadian
standards
concerning
the
implementation of this type where
In conclusion, results had shown
advantage improvement to the
upgrade of windows specifically
when considering the long-cycle
saving.
9
South
7.10
1,226
7,119
16,719
Year to positive cash flow
10
Cumuative cashflow
20
30
Orientation
North
7.20
328
5,621
14,244
West
7.2
735
6,270
15,285
5.b: upgrade DC to TC-Le
West
7.2
735
6,270
15,285
Financial summary
South
9.20
459
7,584
19,192
Year to positive cash flow
After 10 years
Cumuative cashflow
After 20 years
After 30 years
Orientation
North
9.20
(170)
5,641
15,925
West
9.1
392
6,544
17,431
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
35
30
25
20
15
10
5
$
Orientation
North
7.20
328
5,621
14,244
-
Years
South
North
South
West
-
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
35
30
25
20
15
10
5
$
4.a: upgrade DC to DC-le-A
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
-
-
Years
West
South
North
number of results were derived
from the experiment (Figure 4),
(Table 5):
‫ڤ‬summary
In 20 years,SouthforOrientation
an upgrade
to
Financial
North
West
Year to positive cash flow
9.20
9.20
9.1
DC-Le-A,
directing
building
After 10 years
459
(170)
392
Cumuative cashflow
After 20 years
7,584
5,641
6,544
towards
west
resulted
in
After 30 years
19,192
15,925
17,431
reduced cumulative cash flow
with nearly $849 compared to
that of south facing. Likewise,
north facing was reduced
$1498 to that of south facing.
‫ ڤ‬In 20years, for an20,000
upgrade to
18,000
16,000
TC-Le, directing14,000 building
12,000
towards west resulted
in
10,000
8,000
reduced cumulative6,000cash flow
with nearly $1040 4,000
compared to
2,000
that of south facing. Similarly,
35
30
25
20
15
10
5
north
facing was reduced
Years
nearly $1943 to that of south
facing.
‫ ڤ‬The above figures substantially
increased with nearly 65-68%
and when compared after
30years of use.
‫ ڤ‬The year positive to cash flows
were generally similar to the
south facing model in both
upgrades.
$
5.a: upgrade DC to DC-le-A
Financial summary
$
h
7.10
26
19
19
Table (5): Summary of cumulative cash
flow with respect to various orientations
involved
West
4.b: upgrade DC to TC-Le
Figure (4): Regression curves of
cumulative cash flow with respect to
various orientations involved
North
West
In conclusion, the above results
obtained from the modeling south
facing orientation would be more
efficient with respect to passive solar
heating in particular when compared
to that of north. Thus increasing the
number of opening for elevations
facing south is preferable than any
other location. In fact this is valid
for cities locating north the
hemisphere and above the equator.
During summer seasons, treatments
must be applied to apertures on
southern direction to prevent
3. Orientation: The orientation
experiment was run considering
Double-glazed (DC) as a base
model. It is worthy mentioning
that the above experiment
concerning window type was run
considering
south
facing
orientation.
In here, both
upgrades will be examined each
with three different orientations;
south, north and west facing. A
10
overheating within buildings which
will require passive or active cooling
demands.
glazed with double low-e films
are recommended more than
single-glazed or double glazed
windows.
‫ ڤ‬Upgrading
window
from
Double-glazed to DC-Le-A, ,
is more economical if the
window is considered to last
for 20 years and to TC-Le if
replacement would occur after
30 years.
‫ ڤ‬Window design and orientation
are effective for building
designed with passive solar
principles.
7. Conclusions
The prototype dwelling is
designed with considerations to
passive solar heating. Two base
models for window types were
selected and examined using
RetScreen passive solar heating
project model. Building orientations
were examined for three different
orientations including south, west
and north facing. A number of
Conclusions are derived from this
study:
‫ ڤ‬Single-glazed
windows
recorded
the
poorest
performance with respect to
passive solar heating in
buildings.
‫ ڤ‬South facing orientation is
more efficient with respect to
passive solar heating demands
and north facing is less
desirable.
‫ ڤ‬Initial cost of window upgrade
is reimbursed, due to reduction
of active solar heating cost, in
less than ten years depending
on the type of window
selected.
‫ ڤ‬For an economical upgrading
of a windows two issues must
be
considered;
initial
installation fees required for
the upgrade and the project
life.
‫ ڤ‬The use of double-glazed with
a single low-e film plus argon
gas fill and the high
performance IGU is triple-
References
1. Collins, Michael R., Harrison,
Stephen J., 2004 "Estimating the
Solar Heat and Thermal Gain from
a Window with an Interior Venetian
Blind".
pp
486-500,ASHRAE
Trans., , Winter meeting 2004
2. Reilly, S., Hawthorne, W., 1998
"The Impact of Windows on
Residential Energy Use". pp 791798, ASHRAE Trans., Toronto,
Canada 1998.
3. Haung, Y., Mitchell, R., Arasteh,
D., P.E, Selkowitz, S.,
1998
"Residential
Fenestration
Performance
Analysis
Using
RESFEN
3.1",
Thermal
performance of the exterior
envelopes
of
buildings
VII
Symposium, Florida, USA, Dec.,
1998
4. Hechong, L., 2002 "Daylighting
and Human Comfort", pp 65-67,
ASHRAE Journal, Vol.44, no.6,
June 2002.
5. Arasteh, D., P.E., Mitchell, R.,
Kholer, C., Huizenga, C., Curcija,
D., 2001 "Improving Information
Technology,
to
Maximize
11
6.
7.
8.
9.
10.
11.
12.
13.
Fenestration Energy Efficiency".
ASHRAE Trans., , Florida, USA,
December 2001
Enermodal Engineering Limited,
1993, Performance of Windows
Used in the Advanced Houses
Program,
Natural
Resources
Canada,.
RetScreen software, International
Passive Solar Heating Model,
Minister of Natural Resources
Canada 2004.
Henry, R., Dubrous, F., 1998 "Are
Window
Energy
Performance
Selection Requirements in Line
with Product Design in HeatingDominated Climates" ASHRAE
Trans., , Toronto, Canada, 1998
Maghrabi, A., 2005 " Comparative
Study of Alternative Building Walls
and Roofs’ Thermal Insulation in
Makkah, Saudi Arabia, Science,
Engineering And Medical Journal,
Umm Al-Qura University, June
2004 (To be published)
Christian, J.E., 1991 " Thermal
Mass Credit Relating to Building
Envelope Energy Standards", pp
941-957, ASHRAE Trans., Vol. 97,
Part 2.
Maghrabi, A. (1994)" The Transfer
of Adobe Architecture through the
Islamic
World:
Origination,
Transfer and Adaptation", School of
Architecture
and
Planning,
University Of Colorado, USA,
Unpublished
Master
degree
Research.
CLEAN ENERGY PROJECT
ANALYSIS:
RETSCREEN®
ENGINEERING
&
CASES
TEXTBOOK, 2004, Minister of
Natural Resources Canada.
Maghrabi, A. 2000 "Airflow
Characteristics
of
Modulated
Louvered Windows with Reference
to The Rowshan of Jeddah, Saudi
Arabia" School of Architecture and
Urban Planning, University Of
14.
15.
16.
17.
18.
19.
20.
21.
12
Sheffield,
Unpublished
Ph.D.
Thesis.
Etheridge, D. and Sandberg, M.
1996 Building Ventilation: Theory
and Measurements, John Willy &
Sons.
HOT2000 Software, 2000, Minister
of Natural Resources Canada,
(NRCan’s)
Baker, J.A. and Henry, R., (1997)
"Determination of Size-Specific Ufactors and Solar Heat Gain
Coefficients from Rated Values at
Established Sizes – A Simplified
Approach', ASHRAE Transactions
103, Part 1.
Barakat, S.A. and Sander, D.M.,
1982 "Utilization of Solar Gain
Through Windows for Heating
Houses, BR Note No. 184, Division
of Building Research, National
Research Council, Ottawa, ON,
Canada.
Miller, S., McGowan, A. and
Carpenter, S., 1998 "Window
Annual Energy Rating Systems,
ASHRAE Trans., Annual Meeting,
Toronto, ON, Canada, June.
CSA, 1998 "Energy Performance
Evaluation of Windows and Other
Fenestration Systems, Standard
CAN/CSA A440.2", Canadian
Standards Association, 178 Rexdale
Boulevard, Toronto, ON, Canada,
M9W 1R3.
ASHRAE,
Handbook
–
Fundamentals, 1997, American
Society of Heating, Refrigerating
and Air-Conditioning Engineers,
Inc., 1791 Tullie Circle, N.E.,
Atlanta, GA, 30329, USA.
ASHRAE, Applications Handbook,
1995, American Society of Heating,
Refrigerating and Air-Conditioning
Engineers, Inc., 1791 Tullie Circle,
N.E., Atlanta, GA, 30329, USA.
Appendix-a: The various window dimensions examined with respect to
their U and SHGC values.
Orientation
Orientation Elevation
Front
Southٍ
Front
Southٍ
Front
Southٍ
Back
North
Back
North
Back
North
Right
West
Left
East
Left
East
Left
East
Orientation
Orientation Elevation
Front
Southٍ
Front
Southٍ
Front
Southٍ
Back
North
Back
North
Back
North
Right
West
Left
East
Left
East
Left
East
Type
Casement
Fixed
Patio Door
Fixed
Casement
Casement
Patio Door
Fixed
Casement
Casement
Type
Casement
Fixed
Patio Door
Fixed
Casement
Casement
Patio Door
Fixed
Casement
Casement
Height
(mm)
1,600
1,600
2,000
1,600
1,000
1,000
2,000
1,600
1,000
1,600
3
8
2
2
1
1
1
4
1
2
Number
Window Configurations
Width
(mm)
1,000
500
1,200
500
1,600
700
1,000
500
700
1,000
Height
(mm)
1,600
1,600
2,000
1,600
1,000
1,000
2,000
1,600
1,000
1,600
3
8
2
2
1
1
1
4
1
2
Number
Window Configurations
Width
(mm)
1,000
500
1,200
500
1,600
700
1,000
500
700
1,000
Double-glazed, Low-e, Argon (DC-Le-A)
Adjusted
Rated Window
Centre Glazing
SHGC
U-value
SHGC
SHGCcg U-value
Ucg
Total Area
W/(m2-ºC)
W/(m2-ºC)
W/(m2-ºC)
(m2)
0.50
1.90
0.43
2.00
0.64
1.69
4.80
0.51
1.90
0.56
1.82
0.64
1.69
6.40
0.35
1.69
0.31
1.88
0.40
1.41
4.80
0.51
1.90
0.56
1.82
0.64
1.69
1.60
0.50
1.90
0.43
2.00
0.64
1.69
1.60
0.44
1.99
0.43
2.00
0.64
1.69
0.70
0.34
1.72
0.31
1.88
0.40
1.41
2.00
0.51
1.90
0.56
1.82
0.64
1.69
3.20
0.56
1.82
0.56
1.82
0.64
1.69
0.70
0.50
1.90
0.43
2.00
0.64
1.69
3.20
Single glazed clear (SC)
Adjusted
Rated Window
Centre Glazing
SHGC
U-value
SHGC
SHGCcg U-value
Ucg
Total Area
W/(m2-ºC)
W/(m2-ºC)
W/(m2-ºC)
(m2)
0.71
5.40
0.63
5.14
0.86
5.91
4.80
0.69
5.34
0.75
5.55
0.86
5.91
6.40
0.72
5.45
0.63
5.14
0.86
5.91
4.80
0.69
5.34
0.75
5.55
0.86
5.91
1.60
0.71
5.40
0.63
5.14
0.86
5.91
1.60
0.64
5.16
0.63
5.14
0.86
5.91
0.70
0.71
5.39
0.63
5.14
0.86
5.91
2.00
0.69
5.34
0.75
5.55
0.86
5.91
3.20
0.64
5.16
0.63
5.14
0.86
5.91
0.70
0.71
5.40
0.63
5.14
0.86
5.91
3.20
Trible-glazed, Low-e (TC-Le)
Adjusted
Rated Window
Centre Glazing
SHGC
U-value
SHGC
SHGCcg U-value
Ucg
W/(m2-ºC)
W/(m2-ºC)
W/(m2-ºC)
0.45
1.53
0.39
1.68
0.58
1.21
0.53
2.00
0.58
1.88
0.67
1.67
0.32
1.39
0.28
1.60
0.37
1.09
0.47
1.50
0.51
1.39
0.58
1.21
0.45
1.53
0.39
1.68
0.58
1.21
0.40
1.67
0.39
1.68
0.58
1.21
0.31
1.43
0.28
1.60
0.37
1.09
0.47
1.50
0.51
1.39
0.58
1.21
0.40
1.67
0.39
1.68
0.58
1.21
0.45
1.53
0.39
1.68
0.58
1.21
Double-glazed clear (DC)
Adjusted
Rated Window
Centre Glazing
SHGC
U-value
SHGC
SHGCcg U-value
Ucg
W/(m2-ºC)
W/(m2-ºC)
W/(m2-ºC)
0.59
2.73
0.50
2.69
0.76
2.82
0.60
2.76
0.66
2.78
0.76
2.82
0.62
2.85
0.55
2.88
0.73
2.81
0.60
2.76
0.66
2.78
0.76
2.82
0.59
2.73
0.50
2.69
0.76
2.82
0.51
2.69
0.50
2.69
0.76
2.82
0.61
2.86
0.55
2.88
0.73
2.81
0.60
2.76
0.66
2.78
0.76
2.82
0.51
2.69
0.50
2.69
0.76
2.82
0.59
2.73
0.50
2.69
0.76
2.82
13
Appendix-b: Passive Solar Heating energy model flow chart (7).
Adjust window
thermal properties
Calculate base/proposed
heating demands
Calculate base/proposed
cooling demands
Calculate internal gain
Calculate base/proposed
usable solar gains
over heating season
Calculate base/proposed
increase in cooling
loads due to solar gain
Calculate energy savings
Over heating season
Calculate energy savings
Over cooling season
Calculate overall
energy saving
Calculate peak heating
load and peak
cooling load reduction
Appendix-c: General parameters required to run the model.
Shading Factor
Winter shading factor
Summer shading factor
Front
50%
10%
Elevations
Left
Right
15%
30%
10%
80%
Back
60%
80%
Nearest location for weather data of Waterloo
Muskoka,ON
Latitude of project location
°N
44.97
Building front azimuth
°
180
Heating design temperature
°C
-24.2
Cooling design temperature
°C
26.9
Building floor area
m²
110
Mass level (Wood with gypsuim board)
Low
Insulation level
m²·°C/W
4.5
Internal gains
kWh/d
2
Other cost (Contingencies)
%
10
Building has air-conditioning?
No
Heating fuel type
Propane
Modifiy window shading to the propsed case wiondow
No
Avoided cost of energy heating (Propane)
$/L
0.48
Retail price of electricity
$/kWh
0.065
Energy cost escalation rate
%
5
Inflation
%
3
Project Profile
Years
30
Heating system seasonal efficiency
0.9
Elevation
Front Elevation
Left elevation
Right elevation
Back elevation
Installation charges
m2
16.00
7.10
2.00
3.90
29.00
SC
$
$
$
$
$
100
150
150
150
100
14
DC
$
$
$
$
$
175
200
200
200
100
(DC-Le-A)
$
250
$
275
$
275
$
275
$
100
(TC-Le)
$
300
$
320
$
320
$
320
$
100